In fact the whole thing of legilimency and occlumency is based on mental invasion (maybe Harry's poor performance at occlumency lessons is due to his power of the ability to love … I'm not saying he was being loving of Snape LOL, but just that maybe the "ability to love" entails a certain openness that makes occlumency difficult … in other words I am saying it is the ability to love that his mother gave him that makes it this way, not that he always uses that ability, let alone maximizes it).